Generally a digital audio tape player uses a tape cassette 1 as shown in FIGS. 1 and 2. The tape cassette 1 is made of a material such as ABS resin so as to accommodate a magnetic tape. The tape cassette 1 is provided with: a receiving portion 2 having an engaging groove 2a for engaging an engaging roll of a cassette moving section described below, a lid 3 pivotally supported by a shaft at the front of the receiving portion 2, and a slider 4 which adds strength to the lid 3 and slides along the bottom surface of the receiving portion 2. The slider 4 is provided with a first engaging hole 4a for engaging slider lock claw 2b when slider 4 is positioned at the front of cassette 1. The slider lock claw 2b is integrally formed with the receiving portion 2. The slider lock claw 2b presses toward the slider 4 at all times owing to its elasticity, and therefore, if no external force is applied, lock claw 2b engages the first engaging hole 4a. The slider 4 is also provided with a second engaging hole 4b for engaging the slider lock claw 2b when the slider is moved to the rear of cassette 1. In this position, a hole 4c (not shown) of slider 4 corresponds to a tape hub 2c (not shown) around which the tape is wound.
Thus the slider lock claw 2b always presses toward the slider 4 owing to its elasticity, and can be separated from the slider only when an external force is applied. However, if the original elasticity of the slider lock claw 2b is too weak, or if lock claw 2b has lost its elasticity after extended use, the slider lock claw 2b and the first and second engaging holes cannot properly engage. In this case the slider 4 can move into the pivoting track of the lid 3 and impede the closing of the lid. If the lid 3 cannot close, the cassette must be manually removed from the cassette moving section of the tape player which is incapable of ejecting the tape cassette.